DEVELOPING: remove description on tools/munger

Since the changeset of be8503a69d609d0aee844a91f3f5d66f4e2666c7
removed tools/munger directory entirely, those description is stale.

Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Merge pull request #45 from yamahata/delete-munger

DEVELOPING: remove description on tools/munger